Two young Douglas fir were self-pollinated in 1952 and results showed a wide variation in self-incompatibility, one tree producing a fair number of viable seed. It is suggested, that a considerable range of incompatibility following selfing exists within the species and that this is due to some factor that inhibits normal seed development in varying degrees. Cytological examination of material from the highly self-incompatible trees showed that the embryo aborted at an early stage following self-pollination. The harmful effects of inbreeding were clearly seen in the progeny of the one tree, there being highly significant differences in height growth when compared with seedlings resulting from controlled cross- and wind-pollination of the same tree. The importance of the selfing technique and the practical implications of inbreeding are emphasized. A few viable seeds were obtained from unpollinated cones, the resulting seedlings are very uniform, and cytological examination has shown that they are diploid. Further investigations on self-incompatibility and agamospermy in the Douglas fir are being pursued.